The projected negative economy-wide effects of coastal flooding will be relatively small until 2050, but are then predicted to increase substantially towards the end of the century. The findings of a new study recently published on Environmental Research Communications, with the contribution of the CMCC Foundation and EIEE.

Source: adapted from a press release produced by IIASA

The Paris Agreement, adopted in 2015 by 175 parties, aims to limit global warming to well below 2°C compared to pre-industrial levels. However, the period 2010–2020 was the planet’s hottest decade and the long-term trend is upward. Sea level rise is one of the most severe impacts of climate change, with rising waters potentially causing coastal floods, threatening coastal communities, infrastructure, and agriculture.

A new research recently published on Environmental Research Communications for the first time assessed the economy-wide effects of sea level rise when jointly taking into account different mitigation and adaptation assumptions. The study led by Thomas Schinko, IIASA Risk and Resilience Deputy Program Director and co-authored by senior scientists Laurent Drouet (CMCC, EIEE) and Valentina Bosetti (CMCC, EIEE, Università Bocconi di Milano), compared two different climate policy scenarios – one achieving well below 2°C warming by the end of this century, and one overshooting this target – in combination with two different adaptation scenarios (no adaptation and full adaptation to sea level rise) and estimated GDP impacts due to coastal flooding in all scenario combinations for 2050 and 2100.

The study found out that up to 2050 the global GDP losses in both climate futures are similar. However, by 2100, without further adaptation and assuming continued sea level rise, projected annual global economy-wide losses can amount to more than 4%. With ambitious adaptation, this number can be reduced to close to zero, despite the associated costs for adaptation measures and residual impacts. This confirms the importance and economic efficiency of adaptation in the long term: making sure that coastal communities and their infrastructure are climate-resilient will affect the global economy much less than persistent climate impacts.

“In terms of regional effects across the G20”, explains Laurent Drouet, senior scientist at the CMCC Foundation (CMCC) and at the RFF-CMCC European Institute on Economics and the Environment (EIEE), “the highest levels of annual GDP impacts are projected for China. In 2050 and with no further adaptation, economic losses amount to 0.8-1.0%. Estimated GDP losses for India are slightly smaller (0.5-0.6%), followed by Canada (0.3-0.4%).”

Moreover, the study highlighted that until 2050 the direct economic losses of sea level rise on a global level can still be balanced out by international trade and substitution effects in production processes at the macroeconomic level. However, by 2100, the scale of economy-wide effects in G20 countries changes drastically. China remains the country with the highest projected GDP loss if no further adaptation is undertaken, which is now a factor of ten higher than it was in 2050: annual losses amount to 9–10% in a well below 2°C scenario, and to 11-12% under a current mitigation policy scenario. Other regions with severe economy-wide damages by 2100 under no adaptation are Europe and Japan.

However, this changes if stronger mitigation actions are undertaken and sea level rise adaptation efforts are strengthened. Similar to the global picture, all individual G20 countries could thereby limit the residual economy-wide impacts to below 1.0% of GDP if appropriate adaptation measures are taken.

“The findings of this paper demonstrate that we need to think long term”, concludes study lead author Thomas Schinko. The macroeconomic impacts beyond 2050 as a result of coastal flooding due to sea level rise – not taking into account any other climate-related impacts, such as drought – are severe. We, as a global society, need to coordinate mitigation, adaptation, and climate resilient development, and consider where we build cities and situate important infrastructure.”

Reference
Schinko T., Drouet L., Vrontisi Z., Hof A., Hinkel J., Mochizuki J., Bosetti V., Fragkiadakis K., Van Vuuren D., Lincke D. (2019). Economy-wide effects of coastal flooding due to sea level rise: A multi-model simultaneous treatment of mitigation, adaptation, and residual impacts. Environmental Research Communications DOI: https://doi.org/10.1088/2515-7620/ab6368